(1) Field of the Invention
The present invention concerns systems for fixing a part to a bone element, with a particularly advantageous application in the spinal sector, for example for fixing an interbody cage or an intervertebral disk to the vertebral bodies of two consecutive vertebrae.
(2) Prior Art
Intervertebral prostheses which are implanted between the two vertebral bodies of two vertebrae are already known. These prostheses comprise, for example, plates which have to be fixed, respectively, to the two vertebral bodies.
When fixing a part, for example a metal part, to a bone element, and when wanting this part to be immediately integral with this bone element, screws or the like are generally used. It sometimes happens, however, that the location of this part relative to the bone element on which it is to be fixed does not permit the use of screws or the like, because there is insufficient clearance in front of the part relative to the bone element to be able to pre-position the screws before screwing them into the bone element by passing them first through slots or the like made in said part.
To remedy this problem, means such as spikes, ribs, etc., are used which are anchored in the surface part of the bone element. However, in this case the connection between the part and the bone element can only be obtained through natural growth of bone, that is to say by osteosynthesis, by interposing, if necessary, a material which promotes this osteosynthesis, for example hydroxyapatite and/or a porous or nonporous biocompatible material, or similar.
This last solution is not practical because, in this case, the patient in whom such a prosthetic part is implanted has to be told to avoid making excessive movements until definitive connection is obtained through osteosynthesis.